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<refentry id="gnome-vfs-mime-magic-4">
<!-- %Z%%M% %I% %E% SMI; -->
<refmeta><refentrytitle>gnome-vfs-mime-magic.4</refentrytitle><manvolnum>4</manvolnum>
<refmiscinfo class="date">14 May 2008</refmiscinfo>
<refmiscinfo class="sectdesc">&man4;</refmiscinfo>
<refmiscinfo class="software">&release;</refmiscinfo>
<refmiscinfo class="arch">generic</refmiscinfo>
<refmiscinfo class="copyright">&suncopy;</refmiscinfo>
</refmeta>
<indexterm><primary>gnome-vfs-mime-magic</primary></indexterm><indexterm>
<primary>gnome-mime-info</primary></indexterm><indexterm><primary>gnome-mime-keys
</primary></indexterm><indexterm><primary>GNOME VFS MIME detection</primary>
</indexterm><refnamediv id="gnome-vfs-mime-magic-4-name"><refname>gnome-vfs-mime-magic</refname>
GNOME VFS MIME detection</refpurpose></refnamediv>
<refsect1 id="gnome-vfs-mime-magic-4-desc"><title>&desc-tt;</title>
<para>
GnomeVFS is obsolete. Refer to the GNOME Desktop System Administration
Guide for information about how to register MIME type information with
the GNOME desktop. The GNOME Desktop System Administration Guide can
be viewed with
<citerefentry><refentrytitle>yelp</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
</para>
<para>On any modern desktop system, each document type or file type must be
given a unique identification name and icon. In GNOME, this information is
used extensively by the file manager, <citerefentry><refentrytitle>nautilus
</refentrytitle><manvolnum>1</manvolnum></citerefentry>. The primary underlying
mechanism for providing such definitions is achieved via <command>&cmd;</command>. <command>&cmd;</command>
contains the default file content sniffers for identifying MIME types. The
concept of MIME magic is similar to that of Solaris <citerefentry><refentrytitle>
magic</refentrytitle><manvolnum>4</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1 id="gnome-vfs-mime-magic-4-exde"><title>&exde-tt;</title>
<refsect2 id="gnome-vfs-mime-magic-4-exde-cmd"><title>&cmd;</title>
file describes a MIME type. The format of each line is as follows:<screen><computeroutput><replaceable>
offset_start</replaceable>[:<replaceable>offset_end</replaceable>] <replaceable>
pattern_type</replaceable> <replaceable>pattern</replaceable> [&<replaceable>
pattern_mask</replaceable>] <replaceable>mime-type</replaceable></computeroutput></screen></para>
<para>Each line contains the following fields:</para>
<variablelist><varlistentry><term><replaceable>offset_start</replaceable></term>
<listitem><para>Decimal number that, with <replaceable>offset_end</replaceable>,
specifies the bytes offset within the file.</para>
</listitem></varlistentry>
<varlistentry><term><replaceable>offset_end</replaceable></term><listitem>
<para>Decimal number that, with <replaceable>offset_start</replaceable>, specifies
the bytes offset within the file.</para>
</listitem></varlistentry>
<varlistentry><term><replaceable>pattern_type</replaceable></term><listitem>
<para>Can be one of the following types:</para>
<para><literal>byte | short | long | string | date | beshort | belong | bedate
| leshort | lelong | ledate</literal></para>
<para>where <literal>be</literal> stands for Big Endian and <literal>le</literal>
stands for Little Endian.</para>
</listitem></varlistentry>
<varlistentry><term><replaceable>pattern</replaceable></term><listitem><para>
An ASCII string with non-printable characters escaped as hex or octal escape
sequences, and spaces and other important whitespace escaped with a backslash
(<literal>\\</literal>).</para>
</listitem></varlistentry>
<varlistentry><term><replaceable>pattern_mask</replaceable></term><listitem>
<para>A string of hex digits. The mask must be the same specification as the
non-ambiguous patterns.</para>
</listitem></varlistentry>
<varlistentry><term><replaceable>mime-type</replaceable></term><listitem>
<para>A valid MIME type.</para>
</listitem></varlistentry>
</variablelist><para>The magic patterns are matched sequentially from the
first entry to the last entry of the list. Therefore, you should put the non-ambiguous
patterns at the start of the list. Any pattern that requires a deep seek into
the file should be placed at the end of the list to reduce performance overhead.
When designing new document formats, include an easily recognizable unique
magic pattern near the start of the file. A good pattern is is at least four
bytes long and contains one or two non-printable characters so that text files
are not misidentified.</para>
</refsect2>
and gnome-vfs.keys</title>
<para>Apart from file sniffing, GNOME also provide a secondary mechanism to
determine MIME types. If a file has been sniffed and its type does not match
</filename> and processes these. The format of these files is different to
that of pattern magic. Instead of determining the MIME type by reading the
content of the file, the MIME type of the file is determined by its extension.
The mime info file has the following format: <screen><computeroutput><replaceable>
mime_type</replaceable>
ext[,<replaceable>prio</replaceable>]: <replaceable>list of extensions for this mime-type
</replaceable>
regex[,<replaceable>prio</replaceable>]: <replaceable>regular expression that matches the filename
</replaceable></computeroutput></screen></para>
<para>More than one <literal>ext:</literal> and <literal>regex:</literal>
field can be present for a given MIME type. You can also associate a priority
for each field. The default priority (<replaceable>prio</replaceable>) is
1, a higher numerical value indicates a higher priority. The indentation before <literal>
ext:</literal> and <literal>regex:</literal> must be a tab character (<literal>
\\t</literal>). </para>
<para>The searching sequence implies that the magic pattern file has a higher
precedence over the mime info files. As the mime info files are read alphabetically,
this also determines matching orders for the file extension. </para>
ext: foo</computeroutput></screen></para>
ext: foo</computeroutput></screen></para>
first and used.</para>
<para>For each MIME info file there must be an associated keys file in the
same directory. The key file provides human readable text which can be localized
into various languages. The data in these keys files is used by the GNOME
file manager, <citerefentry><refentrytitle>nautilus</refentrytitle><manvolnum>
1</manvolnum></citerefentry>.</para>
</refsect2>
</refsect1>
<refsect1 id="gnome-vfs-mime-magic-4-exam"><title>&exam-tt;</title>
<example role="example"><title>Magic pattern definition for PDF file</title>
</filename> file describes the MIME type of <literal>application/pdf</literal>:<screen><computeroutput>
<para>The first 5 characters of a PDF file are <literal>%PDF-</literal>. The
symbols % and - differentiate the PDF file from a text file.</para>
</example>
<example role="example"><title>Magic pattern definition for BMP file</title>
</filename> file describes the MIME type of <literal>application/bmp</literal>:<screen><computeroutput>
</screen></para>
<para>The interpretation of this line is as follows: <itemizedlist>
<listitem><para>The first two characters are <literal>BM</literal> and the
seventh and eighth characters are NULL.</para></listitem>
<listitem><para>The mask <literal>0xffff00000000ffff</literal> allows the
selction of the first, second, seventh, and eighth characters to be selected
for comparison.</para></listitem>
</itemizedlist></para>
</example>
</title>
ext: Z</computeroutput> </screen></para>
<para>This line indicates that the <literal>x-compress</literal> application
searches for files with a <literal>.Z</literal> extension.</para>
</filename> file is as follows (excluding all localized text): <screen><computeroutput>
description=compress-compressed file
icon_filename=gnome-compressed
default_action_type=application
category=Packages
use_category_default=yes</computeroutput></screen></para>
</example>
</title>
regex,2: tar\.gz$
ext: tgz</computeroutput> </screen></para>
<para>This example uses the priority flag to give <literal>regex</literal>
a higher priority than <literal>ext</literal>, which means that a file with
tgz</literal>.</para>
</example>
</refsect1>
<refsect1 id="gnome-vfs-mime-magic-4-file"><title>&file-tt;</title>
<para>The following files are used by this application:</para>
</term><listitem><para></para>
</listitem></varlistentry>
</term><listitem><para></para>
</listitem></varlistentry>
</term><listitem><para></para>
</listitem></varlistentry>
</filename> </term><listitem><para></para>
</listitem></varlistentry>
</filename> </term><listitem><para></para>
</listitem></varlistentry>
</variablelist></refsect1>
<refsect1 id="gnome-vfs-mime-magic-4-attr"><title>&attr-tt;</title>
<para>See <olink targetdocent="REFMAN5" localinfo="attributes-5"><citerefentry>
<refentrytitle>attributes</refentrytitle><manvolnum>5</manvolnum></citerefentry></olink>
for descriptions of the following attributes:</para>
<informaltable frame="all">
<tgroup cols="2" colsep="1" rowsep="1"><colspec colname="COLSPEC0" colwidth="1*">
<colspec colname="COLSPEC1" colwidth="1*">
<thead>
<row><entry align="center" valign="middle">ATTRIBUTE TYPE</entry><entry align="center"
valign="middle">ATTRIBUTE VALUE</entry></row>
</thead>
<tbody>
</row>
<row><entry colname="COLSPEC0"><para>Interface stability</para></entry><entry
colname="COLSPEC1"><para>Obsolete Volatile</para></entry></row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 id="gnome-vfs-mime-magic-4-also"><title>&also-tt;</title>
<!--Reference to another man page-->
<!--Reference to a Help manual-->
<!--Reference to a book.-->
<para>
<citerefentry><refentrytitle>nautilus</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>gnome-vfs.applications</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
<citerefentry><refentrytitle>libgnomevfs-2</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>gnome-interfaces</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
<para>
Latest version of the
<citetitle>GNOME Desktop System Administration Guide</citetitle>
for your platform.
</para>
</refsect1>
<refsect1 id="gnome-vfs-mime-magic-4-note"><title></title>
<para>Written by Ghee Teo, Sun Microsystems Inc., 2003.</para>
</refsect1>
</refentry>